Marine sliding bearings re prone to wear in harsh environments. A real-time in-situ measurement method of sliding bearing wear, based on chirped fiber Bragg grating (CFBG), was proposed. The CFBG wear detection sensor and the corresponding demodulation system were designed and fabricated. The CFBG was sealed to ensure that wear synchronously with the sliding bearing. The relationship between the bandwidth and length of the CFBG was established and adopted to calculate the wear length. Meanwhile, a Savitzky–Golay filter was applied to denoising to improve the accuracy of the demodulation system. Experimental results showed that the sensor could achieve high precision real-time bearing detection and fault warning. With a chirp rate of 10 nm / cm and a bandwidth resolution of 20 pm, a wear range >8 mm and an accuracy of 0.3 mm could be obtained.